Improvement in screw-cutting machines



G. GpWALWORTH;

1 Screw-Cutting Machines.

No. 141,299, PatgntedJuly 29,1873.

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AM. PHOTO-LITHOGRAPH/C co. N.Y(0sBoRN5's mums) NITED STATES PATENTOFFICE.-

OALEB O. WALWORTH, OF BOSTON, MASSACHUSETTS.

IMPROVEMENT IN SCREW-CUTTING MACHINES.

Specification forming part of Letters Patent No. 141,299, dated July 29,1873; application filed February 27, 1873.

To all whom it may concern:

Be it known that I, CALEB O. WALwoRTH, of Boston, in the county ofSuifolk and State of Massachusetts, have invented an Improvement inScrew-Cutting Lathes; and I do hereby declare that the following, takenin connection with the drawings which accompany and form part of thisspecification, is a description of my invention sufficient to enablethose skilled in the art to practice it.

The invention relates to a method of letting back the tool of ascrew-cutting lathe when the nut has been turned back at the completionof the operation of the tool, so as to enable the work to be releasedwithout screwing back the tool after it leaves the work. For thispurpose I combine with the rotating feedscrew, to which thetool-carrying spindle is made fast, and the stationary nut, in whichsaid screw turns to effect the feed and return movements of the tool, alocking and relief mechanism, by which the nut is held fast in positionduring the forward and return movements of the tool, and by which it maybe unlocked or disengaged and slipped back when the tool is withdrawnfrom the screw cut by it. It is in this provision that the inventionconsists.

The drawing represents, in sectional elevation and in end view, thearrangement of mechanism embodying my invention.

(6 denotes the tool-spindle, splined to and slidin g in a rotating box,1), extending through and fixed to the feed-screw 0. The box b rotatesin a bearing, d, in the rear extension 0 of which is supported the nutf, in which rotates the screw 0, the said nut being stationary for theworking of the tool, and effecting the forward or feed movement of thetool and the return movement thereof as the spindle is rotated. Insteadof making the nut immovable, it is locked in position for the working ofthe tool, and is made capable of a short back movement, so that, byreleasing the locking mechanism when the tool has been drawn back farenough to clear the screwthread out by it, the not with the spindleattached to it can be thrown back so as to clear the cutting-tool fromits work-far enough to allow the work to be removed or new workintroduced without waiting to screw back the tool further. The nut isheld or locked by a weighted pawl, g, the tooth of which slips by ashoulder, h, at the under side of the not. In a slot, t, made in theunder surface of the nut is a slide, it, which ispivoted at one end to alever, l, as seen in the drawing. The opposite end of the slide ischamfered or inclined, so that, if the slide be thrown back by the leverZ, the incline will slide under the pawl-tooth and move it from theshoulder h, while, if moved in the opposite direction, the pawl-tooth,by the weight of its outer end m, will be carried into engagement withthe shoulder. The lever Z is connected to the nut f by a pin, 0,extending through a slot, n, in the lever, and through cars 19 extendingfrom the nut and when the lever is moved to release and throw back thenut, the slot 11. ena- I bles the lever to first start the slide anddisengage the pawl, and then, acting against the pin 0, to slide backthe nut, and with the not the screw 0, spindle a, and cutting-tool.These movements are eli'ccted as soon as the tool, in turning back fromthe screw-thread cut by it, passes out of action with such screw-thread.For reception and -action of the pawl g and lever-slide k, a slot, q, isout through the bearing or sleeve d.

I claim- In combination with feed-screw and its toolcarrying spindle,the nut f, pawl g, lever l, and slide 70, substantially as described. 7

CALEB O. WALWORTH.

Witnesses FRANCIS GOULD, M. W. FROTHING-IIAJI.

